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ESTE2016 Detrapping in persistent phosphors
The document discusses advancements in persistent phosphors, highlighting the role of thermally, mechanically, and optically driven release mechanisms in their performance. It presents findings on the influence of excitation intensity and trapping dynamics, emphasizing challenges and potential applications in imaging and energy storage. The study suggests that both optically stimulated and mechanoluminescent materials offer valuable insights for enhancing phosphor functionality.
ESTE2016 Detrapping in persistent phosphors
- 1. ugent.be lumilab.ugent.be nb-photonics.ugent.be Persistentphosphors beyond the afterglow: optical and mechanical detrapping ESTE2016 – 6th International Conference on Excited States of Transition Elements Polanica Zdrój, Poland – Augustus 23 2016 Philippe F. Smet Claude Tydtgat, Dirk Poelman, Katrien W. Meert, Simon Michels, Mathias Kersemans philippe.smet@ugent.be @pfsmet 1
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- 3. The game changingpersistent phosphor: SrAl2O4:Eu,Dy Van den Eeckhout K. et al, Materials 3 (2010) 2536-2566 Persistent Luminescence in Eu2+-Doped Compounds: A Review
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- 5. @pfsmet thermally, mechanically or opticallydriven release
- 6. I (cd/m²) Time aftersunset (h) Thermally driven (uncontrolled) release DT = 0°C DT = -10°C DT = -20°C Botterman et al, Optics Express 23 (2015) A868 Persistent phosphor SrAl2O4:Eu,Dy in outdoor conditions: saved by the trap distribution
- 7. @pfsmet Back of theenvelope calculation Accessible traps: 10% of recombination centers 2% molar doping by Eu in SrAl2O4 Alkaline battery: 407 J/g Charging (filling of traps) Decharging (emptying of traps)
- 8. New persistent phosphorswere developed (which are sometimes not even visible to the human eye) T. Maldiney et al., Nat. Mater. 13, 418–426 (2014), “The in vivo activation of persistent nanophosphors for optical imaging of vascularization, tumours and grafted cells”
- 9. Botterman et al.,Acta Materialia 60 (2012) 5494-5500 Mechanoluminescence in BaSi2O2N2:Eu BaSi2O2N2:Eu Mechanically driven release
- 10. Whatever the application( ), energy storage capacity is crucial. Where is the bottleneck? @pfsmet
- 11. Charging CaAl2O4:Eu,Nd The trappingprobability is very, very high. Afterglow … > 72 hours
- 12. How can weunite • a (relatively) low storage capacity • a very high trapping efficiency ? One possible approach: Modelling trapping and detrapping simultaneously
- 13. The experiment... inorder to understand (de)trapping Variation 193K to 353K Jonas Botterman et al, Physical Review B 90, 085147 (2014) Trapping and detrapping in SrAl2O4:Eu,Dy persistent phosphors: Influence of excitation…
- 14. Simple system (oneEu site) – Sr2MgSi2O7:Eu,Dy Charging | Afterglow | TL analysis TL cannot be explained by single trap depth
- 15. Setting up themodel: keep it simple & local Eu2+ Trap + e Eu3+ Empty trap Detrapping Claude Tydtgat et al, Optical Materials Express 6 (2016) 844-858 Optically stimulated detrapping during charging of persistent phosphors
- 16. pnr • Boundary conditionsfor charging and afterglow • pe (excitation rate) is small • Two solutions l1 and l2: two exponentials Differential equations Eu2+ trap
- 17. • pe 0 : Eigenvalues for charging and afterglow are • Solution for charging: charging afterglow @pfsmet
- 18. Adding distribution fortrap depths Claude Tydtgat et al, Optical Materials Express 6 (2016) 844-858 Optically stimulated detrapping during charging of persistent phosphors Eu2+ traps
- 19. Problem #1 Step incharging curve ≠ Step for afterglow Charging | Afterglow | TL analysis Simple system (one Eu site) Sr2MgSi2O7:Eu,Dy
- 20. Charging | Afterglow| TL analysis Problem #2 Eigenvalues are identical for different pe ≠ Charging dynamics strongly depend on pe
- 21. Problem #3 Absorption pe(M-me-m) should decrease <> Absorption increases, depends on pe Reflected excitation light
- 22. Influence of excitationrate pe not negligible, on the contrary! Large influence, yet pe is low Effect is proportional to pe x a OSL : a pe Claude Tydtgat et al, Optical Materials Express 6 (2016) 844-858 Optically stimulated detrapping during charging of persistent phosphors Eu2+ traps
- 23. It makes sensefor charging and decharging… Emission intensity a = 200 Claude Tydtgat et al, Optical Materials Express 6 (2016) 844-858 Optically stimulated detrapping during charging of persistent phosphors Charging | Afterglow
- 24. … and forthe influence of the excitation intensity pe Claude Tydtgat et al, Optical Materials Express 6 (2016) 844-858 Optically stimulated detrapping during charging of persistent phosphors
- 25. 25 -60°C 0°C TL Heating Empty all traps 0 10 20 30 -50-25 0 25 50 75 100 TLintensity(arb.units) Temperature (°C) 100%
- 26. 26 -60°C 0°C TL Heating Empty all traps 100%1% 60% Thermal barrier for trapping
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- 28. OSL (at chargingl) is compatible with: • Different initial rise and drop after charging • Exponentials for charging and afterglow are different • Absorption increases during charging • Influence of excitation intensity • Charging behaviour depends on wavelength (via abs) • Different trap filling for different wavelengths This is worrying/hopeful for applications… … and requires careful study!
- 29. Part 2: Mechanicallydriven release C.-N. Xu et al. N. Terasaki and C.-N. Xu, IEEE Sens. J., 2013, 13, 3999.
- 30. Kersemans et al,Applied Physics Letters 107 (2015) 234102 Fast Reconstruction of a Bounded Ultrasonic Beam using Acoustically induced Piezoluminescence Part 2: Mechanically driven release BaSi2O2N2:Eu2+
- 31. Kersemans et al,Applied Physics Letters 107 (2015) 234102 Fast Reconstruction of a Bounded Ultrasonic Beam using Acoustically induced Piezoluminescence Part 2: Mechanically driven release
- 32. 32 Ultra- sound Competition with thermaldetrapping Linear response to ultrasound power Kersemans et al, Applied Physics Letters 107 (2015) 234102 Fast Reconstruction of a Bounded Ultrasonic Beam using Acoustically induced Piezoluminescence
- 33. 33 Imaging of USpressure field by Acoustically induced Piezoluminescence Kersemans et al, Applied Physics Letters 107 (2015) 234102 Fast Reconstruction of a Bounded Ultrasonic Beam using Acoustically induced Piezoluminescence
- 34. 34 0 Transducer Increasing distancez (mm) 100 200 300 Kersemans et al, Applied Physics Letters 107 (2015) 234102 Fast Reconstruction of a Bounded Ultrasonic Beam using Acoustically induced Piezoluminescence
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- 36. 2cm Towards a fast,full 3D reconstruction of ultrasound beams Kersemans et al, Applied Physics Letters 107 (2015) 234102 Fast Reconstruction of a Bounded Ultrasonic Beam using Acoustically induced Piezoluminescence
- 37. Conclusions. 1. In persistentphosphors, optically stimulated detrapping occurs also at excitation wavelength, limiting the trapping capacity. 2. Mechanoluminescent phosphors can be used to map ultrasound pressure.
- 38. Resources Feature issue onPersistent and Photostimulable Phosphors in Optical Materials Express (published March 2016) http://tiny.cc/OMEXPPP
- 39. Chapter Persistent Phosphors Handbook onthe Physics and Chemistry of Rare Earths Volume 48, Chapter 274 (2015) 1 - 108
- 40. Resources & Acknowledgments Thankyou for your attention ! (and your feedback…) Presentation can be found at http://www.slideshare.net/pfsmet